Why is the loop cut tool stopping at one face?
I don't fully understand your question, but keep in mind that loop cutting only works in quads. What you seem to have there is an "ngon" ==> An ngon is a face or polygon that is made up of five or more sides or edges connected by five or more vertices. Anything over a quad (4 sides) is considered an ngon. So notice in your screenshots that the loop cut worked perfectly where you had faces with 4 vertices and (if what I am seeing is correct) where the interruption happens you have a face with 7 vertices. Try joining the 2 vertices above the ?pipe? by selecting them and pressing "J".